Lecture 10: Reproductive Toxicants and Induced Abortion

nitrates

• nitrate accumulating plants

• johnson grass, sudan grass, oats, wheat, corn

• exposure to fertilizers

• especially seen in drought periods

• methemoglobinemia

• fetal hypoxia and death

• late gestation abortions

• diagnosis is testing ocular fluid of abortus

ponderosa pine

• pinus ponderosa

• isocupressic acid

• vasoconstriction at caruncles

• hemorrhagic placentitis

• up to 50% abortion rate in cattle grazing pine needles

• diagnosis based on history of ingestion and circumstantial evidence

locoweed

• astragalus and oxytropis spp.

• swainsonine

• can cause neurologic signs, abortion, fetal abnormalities like hydrops/arthrogryposis

• up to 40% of cattle grazing may abort

• cattle get hooked and can’t quit

• diagnosis based on circumstantial evidence

• causes more economic losses than any other plant

broomweed or snakeweed

• gutierrezia spp.

• mono and di-terpenes

• abortion and retained fetal membranes

• spring

fescue

• festuca arundinacea infected with fungus neotyphodium coenophialum

• produce toxic alkaloids → ergovaline

• causes peripheral vasoconstriction fescue foot

• summer slump in cattle

• causes fat necrosis throughout the body

• rotate off of fescue in summer

• re-plant pastures

• avoid seedhead grazing

summer slump from fescue

• decreased repro efficiency/infertility

• embryo’s fertilized with semen from bulls grazing infected fescue have been shown to lack the ability to develop

• decreased milk

why would you induce abortion?

• accidental breeding of young heifers

• pregnancy in feedlot heifer

• fetal maceration

• fetal mummification

• hydrops conditions

what is this showing?

removal of mummy by colpotomy

what is this showing?

hydrops

progesterone sources in cattle

• corpus luteum ovulation to term

• placenta is an additional source 150-250 days gestation

• CL final month of gestation → placental progesterone declines during this time

• the goal is to target the source of progesterone that is appropriate for the stage of gestation at time of induction of abortion

drugs used to induce abortion in cattle

• prostaglandin F2a → dinoprost (lutalyse), cloprostenol (estrumate)

• corticosteroids → dexamethasone

mode of action of PGF2a

• causes luteolysis

• CL does not respond to PGF2a before day 5-6 post-ovulation

• has no effect on placental progesterone production

mode of action of corticosteroids

• reduce placental progesterone production

• no effect on the CL

abortion strategy for 5-150 days of gestation

• single injection of PGF2a

• abortion in 5-7 days

• fertile estrus 3-5 days later

abortion strategy for 30 and 120 days of gestation

• pregnancy can be manually disrupted

• may take 3-4 weeks for abortion to occur

• this can be difficult

abortion strategy for 150-240 days of gestation

• must remove ovarian and placental progesterone

• combination of corticosteroids and PGF2a required

• 95% efficacious with abortion in 5 days

• treatment of choice is unknown

abortion after 120 days of gestation leads to

RFM in 80% of cows treated → membranes are usually lost within 7 days

4% of heifers treated in feedlot will develop

fetal mummification